duplus

Latin

**Latin numbers ^(edit)**
	20^{[a], [b], [c]}
← 1	II 2	3 →
Cardinal: duo Ordinal: secundus, alter Adverbial: bis Proportional: duplus Multiplier: duplex, alterplex, biplex Distributive: bīnus Collective: bīniō Fractional: dīmidius, sēmis

Inherited from Proto-Italic *duplos. By surface analysis, duo +‎ -plus.^[1] Cf. Ancient Greek διπλόος (diplóos, “double”), from δι- (di-), from δύο (dúo, “two”), + -πλόος (-plóos, “-fold”), and Proto-Germanic *twīflaz (“doubt”).

duplus (feminine dupla, neuter duplum); first/second-declension adjective

	masculine	feminine	neuter	masculine	feminine	neuter
	singular		plural
nominative	duplus	dupla	duplum	duplī	duplae	dupla
genitive	duplī	duplae	duplī	duplōrum	duplārum	duplōrum
dative	duplō	duplae	duplō	duplīs
accusative	duplum	duplam	duplum	duplōs	duplās	dupla
ablative	duplō	duplā	duplō	duplīs
vocative	duple	dupla	duplum	duplī	duplae	dupla

Italo-Dalmatian:
- Italian: doppio
  - → Sardinian: dopiu
  - → Sicilian: doppiu
- Venetan: dopio, dupio
Rhaeto-Romance:
- Friulian: dopli
- Romansh: dubel, dobel
Gallo-Italic:
- Ligurian: doggio
- Lombard: dopi
- Piedmontese: dobi
Gallo-Romance:
- Catalan: doble
- Franco-Provençal: doblo
- Occitan: doble
- Old French: doble (see there for further descendants)
Ibero-Romance: (terms with 'e' endings may be from duplex)
- Asturian: doble, duble, doblu, dublu
- Old Galician-Portuguese: dobro
  - Galician: dobre
  - Portuguese: dobre, dobro
- Spanish: doble, doblo

Borrowings:

^ De Vaan, Michiel (2008), “-plus”, in Etymological Dictionary of Latin and the other Italic Languages (Leiden Indo-European Etymological Dictionary Series; 7), Leiden, Boston: Brill, →ISBN, page 475: “Derivatives > line 1 > duplus”